Discovering Demetra+

This document is not a systematic description of Demetra+. Its only aim is to give some feeling on the software by outlining some features, through small examples.

The first paragraph is based on the description of general tools available in the software. The second one consider Tramo-Seats single processing, the third one focuses on X12 and the last paragraph considers multi-processing (batch processing).

General features

Calendars

The calendars of Demetra+ simply correspond to the usual trading days contrasts variables, based on the Gregorian calendar, modified to take into account some specific holidays. Those holidays are handled as "Sundays" and the variables are properly adjusted to take into account long term mean effects.

The list of the user-defined variables can be edited by means of the main menu item "Workspace -> Edit ->Calendars"

Demetra+ considers three kinds of calendars:

National calendars, identified by specific days Composite calendars, defined as weighted sum of other calendars Chained calendars, defined by two other calendars and a break date

The calendars can be defined recursively.

The data generated by each calendar can be viewed by a double click on the corresponding item in the workspace tree.

The regression variables can be generated for any frequency and any (reasonable) time span through that window; the periodogram of those series are displayed when a column is selected.

Finally, the series can be copied by drag (see blue circle) and drop or through the local menu to other places/software

User-defined regression variables

User-defined regression variables are simply time series identified by their name. Those names will be used in other parts of the software (regression) as identifier of the data.

The list of the user-defined variables can be edited by means of the main menu item "Workspace -> Edit ->User variables"

Demetra+ considers two kinds of user-defined regression variables:

Static variables, usually imported from external software Dynamic variables, coming from some browser.

Static variables imported from external software (for instance Excel) must be formatted as defined in the "Quick Start" document. They are imported by drag and drop or using the usual keys (ctrl-v).

Dynamic variables are imported by drag and drop from a browser of the application.

The figures of static variables cannot be changed. Currently, the only way to update static series consists in removing them from the list and to re-import them with the same names as previously.

Dynamic variables are automatically updated each time the application is re-opened. So, they should be the preferred way to handle user variables.

The names of the series can be changed as usual (selected a series and click once again when it has been selected). The selected series can be showed in a small chart window by a double click.

Tramo-Seats processing

X12 processing

For the examples on X12 processing, we will use the "unempoyment.xml" xml file, in the "My Documents\Data\Xml" folder provided with the installation procedure. The series provided in that file come from the Belgian unemployment statistics.

The series are loaded using the following procedure:

Select the "Xml" tab in the browsers panel Click on the "Open" button Choose the file

Select the specification

In the navigation panel of the current workspace, select the active X12 specification

Select in the tree the specification you want to select Open the local menu by means of the right button of

the mouse Choose the "Active" menu item

For a description of the different default specification, you should refer to the "Demetra+ Quick Start" document.

Launch the processing

The X12 algorithm is launched by a double click on a series in the browser panel

The results are displayed in a window that contains many detailed panels. The user can go through them by selecting a node in the navigation tree of the X12 processing. The current specification and the current series are displayed on the top of the window.

Launching several processing

Demetra+ provides a multiple documents interface (MDI). The user can display and compare many documents.

He/she can process as follows:

Select another active specification (for instance, "RSA1"), following the procedure described above

Double click on a series in the browsers panel Make some place by clicking on either the "Auto

Hide" (red) button or the "Close" (blue) button of the system windows ("Workspace", "Logs", "TSProperties").

Tile the output windows through the "Window" sub-menu

New double click in the browsers will update the different processing (that feature can be disabled by locking a given processing, through the "X12Doc-xxx" -> "Lock" main menu item.

The procedure described above can be used with any specification (Tramo-Seats and X12)

The next steps will consider the interaction with a specific processing. Close one of the previous windows and maximize the other.

Inspecting the results

Zooming the main charts

Many charts of Demetra+ provide zooming features. Select the zone you want to zoom with your mouse (from the top-left corner to the bottom-right one). Select any rectangle from bottom-right to top-left to un-zoom the chart.

You can move (red) or resize (blue) the selected zooming window with the scroll bars. You can also highlight any series by clicking on it.

Displaying the SI ratio

The SI-ratio chart is available under the "Main results" node. You can enlarge a specific period by clicking in its zone. The details are displayed in a resizable pop-up window.

Modifying the specification

The current specification can be displayed by means of the main menu item: "X12Doc-xxx" -> "Specification" -> "Current specification".

It is displayed in a non modal dialog box, so the user can change any option and inspect its impact on the results. For a detailed description of the X12 specifications, you should refer to the "Demetra_Spec.docx" document.

For example:

Select in the output window the 'Main results -> Charts" window Modify the span of the series in the "Basic" panel:

o Click on the Basic item in the left panel of the specification dialog boxo Expand the "series span" node in the right panelo Choose the "excluding" selection type o Write "12" in the "last" node

Press the "Apply" button

The processing is computed on the series without the last 12 observations. A visual comparison of the forecasts of X12 and of the actual figures is displayed on the chart.

Some other examples are explained below. They are based on series coming from the "prod.xml" file, which provide more eloquent results. The next snapshots use the series named "Industries manufacturières"

Suppressing of trading days

The trading days regression variables can be suppressed by setting the "Trading days -> Type" to "None" in the "Calendar effects" panel of the specification dialog box.

Meaningful information is provided in the "Pre-processing -> Arima" panel

or in the different panels of the spectral analysis

Changing X11 options

The X11 panel of the specification dialog box contains a rich set of options on the X11 decomposition. Their effects appear - for instance - in the SI-ratio chart

The previous snapshot was realized by setting the "Use forecasts" option on false and the "Seasonal filter" on "S3x15"

Interaction with other tools

The different series that appear in the results can be dropped in other windows of Demetra+

Useful examples are described below:

Open auto-regressive spectrum windows using the following main menu item: "Tools -> Spectral Analysis -> Auto-regressive spectrum"

Drop meaningful series of the results in those tool windows (for example "A1" and "B1" from the "Decomposition (X11)" sub-nodes.

Open a "growth chart" using the following main menu item: "Tools -> Tool Windows -> Growth chart"

Drop D11 (for example) in it.

The different tool windows are dynamically updated when:

A new series is selected, through a double click in the browsers panel or when a series is dropped in the left zone of the X12 window.

The specification is changed, by means of the specification dialog box or when another specification, coming from the workspace, is dropped in the left zone of the X12 window.

Many other combinations are of course possible.

It should be noted that the current implementation is not able to detect recursive processing, obtained for instance by dropping a series like "D11" in the left zone of the same X12 window. Such an attempt will generate a crash of Demetra+.

Other features of X12 processing

Amongst the numerous features provided by the X12 output window/specification, we would like to mention the following ones.

Revision history

In the revisions history panels (which display the initial estimates in blue points and the last estimates in red lines), the user can have a complete overview of the different revisions for a given

time span by selecting with the mouse (just like for zooming) the considered periods. The successive estimation are displayed in a separate pop-up window

He/she can also get all the revisions for a specific period by clicking on the point that corresponds to the first estimate for that period. The results of those popup-up windows can be copied or drag and dropped to other software (Excel...)

By default, the revisions are obtained with the same model, but in re-estimating its parameters. That option can be changed through the local menu of the revision history node (left panel), at the expense of the speed of the processing and for results that are usually very similar.

Stability of the model

The X12 output window provides some purely descriptive features to analyze the stability of some part of the model. For instance, the coefficients of the trading days variables computed by means of a moving window (by default on 8 years, using the same model but with re-estimated parameters) are displayed in the panel corresponding to the "Model stability -> Trading days" node.

User-defined regression variables

Once calendar variables and/or user-defined regression variables have been defined (see general features), they can be integrated in the regression model of X12 using several ways.

Calendars can be chosen in the trading days node of the calendar effects panel of the specification dialog box:

Select the option "Calendar" in the "Type" field Choose the holiday in the list that is automatically displayed (it corresponds to the calendars

defined in the workspace; calendars must be defined to get access to that option). The corresponding calendar variables are computed "on the fly".

Trading days effects can also be defined in a free way as pure user-defined regression variables:

Select the option "UserDefined" in the "Type" field Choose the variables in the list that is displayed after a click on the dots on the right of the

"Details -> Items" row (it corresponds to the user variables defined in the workspace; user variables must be defined to get access to that option).

Regression variables that are not considered as trading days can be integrated in a quite similar way through the regression panel of the specification dialog box.

Multi-processing